The same color illusion — also known as Adelson’s checker shadow illusion, checker shadow illusion and checker shadow — is an optical illusion published by Ted Adelson in 1995. The squares A and B on the illusion are of the same color (or shade), although they seem to be different.

"When interpreted as a 3-dimensional scene, our visual system immediately estimates a lighting vector and uses this to judge the property of the material."[1]